What makes something absurd?

I was browsing reddit yesterday when I came across a photo of a postcard. It had a pumpkin juxtaposed over a shoreline:

I found it odd, what was it about the composition of this postcard that made it absurd? What is it that makes an absurd piece absurd? I thought to myself: Was it the non sequitur logic between the elements? But then I realized that absurd art can have a certain logic to it, and that art can make no logical sense, but still not be absurd. So what was it that made it absurd?

I asked a friend about it, telling him what I have told you, and had this to say about it: “… I think it’s the anachronistic nature of it. Pumpkins = fall beaches = warm months. That and the composition, with the pumpking taking p a good lot of the image [acts] almost like a self portrait”

I’m still perplexted by it, but it was an interesting thought experiment none the less.